Transcript Space 1.1

The streak of light in the photograph above was
produced by a tiny particle from space burning
up in Earth’s atmosphere. Shown to the left is
Barringer Crater in Arizona.
Shown at left is the Arecibo telescope. Data
collected with the telescope were used to
make this model of the asteroid Toutatis.
Before, you learned
• Earth is one of 8 planets that orbit
the sun
• The Moon orbits Earth
• Earth turns on its axis every 24
hours
Now, you will learn
• How the universe is arranged
• How stars form patterns in the sky
• How the motions of bodies in
space appear from Earth
VOCABULARY
orbit, solar system, galaxy, universe,
constellation
Magnet Word Diagram= Include: definition,
example(s), picture, pronounce, origin,
sentence, synonyms, fun facts.
We see patterns in the universe.
For most of history, people had very limited
knowledge of space. They saw planets and stars as
points of light in the night sky. However, they did not
know how far those bodies were from Earth or from
each other. Early observers made guesses about
planets and stars on the basis of their appearance
and the ways they seemed to move in the sky.
Different peoples around the world connected the
patterns they saw in the sky with stories about
imaginary beings.
We still have much to learn about the universe.
Within the last few hundred years, however, new
tools and scientific theories have greatly increased
our knowledge. In this unit you will learn about the
arrangement of planets and stars. You will also learn
about the ways in which astronomers explore and
study space.
Arrangement of the Universe
If you look up at the sky on a clear night, you
will see only a tiny fraction of the planets and
stars that exist. The number of objects in the
universe and the distances between them are
greater than most people can imagine. Yet these
objects are not spread around randomly. Gravity
causes objects in space to be grouped together
in different ways.
The images show some basic structures in the
universe. Like a camera lens zooming out, the
images provide views of space at different levels
of size.
1. Planets/Earth Our planet's diameter is
about 13,000 kilometers (8000 mi). This is
almost four times the diameter of the
Moon, which orbits Earth. An orbit is the
path of an object in space as it moves
around another object because of gravity.
2. Solar System(s) Earth and eight other major
planets orbit the Sun. The Sun, the planets,
and various smaller bodies make up our
solar system. The Sun is about 100 times
greater in diameter than Earth. You could…
Tip: The word orbit can be a noun or a verb.
fit more than 4000 bodies the size of the Sun
between the Sun and the solar system's
outermost planet at its average distance from
the Sun. The Sun is one of countless stars in
space. Astronomers have detected planets
orbiting some of these other stars.
3. The Milky Way/Galaxies Our solar system and
the stars you can see with your bare eyes are
part of a galaxy called the Milky Way. A galaxy is
a group of millions or billions of stars held
together by their own gravity. If the solar system
were the size of a penny, the Milky Way would
stretch from Chicago to Dallas. Most stars in the
Milky Way are so far away that our galaxy
appears to us as a hazy band of light.
4. The Universe The universe is everything—space
and all the matter and energy in it. The Milky
Way is just one of many billions of galaxies in the
universe. These galaxies extend in all directions.
Astronomers study space at each of these different
levels. Some focus on planets in the solar system.
Other astronomers study distant galaxies. To learn
how the universe formed, astronomers even study
the smallest particles that make up all matter.
What is the relationship between the
solar system and the Milky Way?
Website:
http://scaleofuniverse.com/
Constellations
If you want to find a particular place in the United
States, it helps to know the name of the state it is in.
Astronomers use a similar system to describe the
locations of objects in the sky. They have divided the
sky into 88 areas named for the constellations.
A constellation is a group of stars that form a pattern
in the sky. In the constellation Cygnus, for example, a
group of bright stars form the shape of a flying swan.
Any other objects in that area of the sky, such as
galaxies, are said to be located in Cygnus, even if they
are not parts of the swan pattern. The ancient Greeks
named many of the constellations for animals and
imaginary beings.
Unlike the planets in the solar system, the stars in a
constellation are usually not really close to each
other. They seem to be grouped together when
viewed from Earth. But as the illustration above
shows, you would not see the same pattern in the
stars if you viewed them from another angle.
What relationship exists among the stars in
a constellation? (Look at next slide;)
Visualization:
Click Here and Observe the Night Sky - Animation
The sky seems to turn as Earth rotates.
You cannot see all of the constellations at
once, because Earth blocks half of space from
your view. However, you can see a parade of
constellations each night as Earth rotates. As
some constellations slowly come into view
over the eastern horizon, others pass high in
the sky above you, and still others set at the
western horizon. Throughout the ages, many
peoples have observed these changes and
used them to help in navigation and measuring
time.
If you extended the North Pole into space, it
would point almost exactly to a star called
Polaris, or the North Star. If you were standing
at the North Pole, Polaris would be directly
over your head. As Earth rotates through the
night, the stars close to Polaris seem to move
in circles around it. Although not the brightest
star in the sky, Polaris is fairly bright and easy
to find. You can use Polaris to figure out
direction and location.
What causes constellations to change positions
during the night?
The movements of planets and other nearby objects
are visible from Earth.
A jet plane travels at a greater speed and altitude
than a bird. Yet if a bird and a plane flew overhead at
the same time, you might think that the bird was
faster. You would have this impression because the
farther away a moving object is from you, the less it
seems to move.
Stars are always moving, but they are so far away that
you cannot see their movements. Observers have
seen the same constellation patterns for thousands of
years. Only over a much longer period does the
motion of stars gradually change constellation
patterns.
By contrast, the Moon moves across the star
background a distance equal to its width every hour
as it orbits Earth. The Moon is our closest neighbor.
The planets are farther away, but you can see their
gradual movements among the constellations over a
period of weeks or months.
Planet comes from a Greek word that means
"wanderer." Ancient Greek astronomers used
this term because they noticed that planets
move among the constellations. It is easiest to
see the movements of Venus and Mars, the two
planets closest to Earth. They change their
positions in the sky from night to night.
The apparent movement of the sky led early
astronomers to believe that Earth was at the
center of the universe. Later astronomers
discovered that Earth and the other planets
orbit the Sun. The timeline on pages 72–75
introduces some of the astronomers who helped
discover how planets really move in the solar
system.
Ptolemy’s Geocentric Model
Galileo
Galilei
Copernicus’ Heliocentric Model
The Cosmic Web of the Universe
Voids
Superclusters = Small galaxy groups
KEY CONCEPTS
1. What are the basic structures in which objects are
grouped together in space?
2. What is a constellation?
3. How does Earth's rotation affect our view of
stars?
CRITICAL THINKING
4. Compare and Contrast How is the grouping of stars in a
constellation different from the grouping of planets in the
solar system?
5. Apply The planet Jupiter is farther than Mars from Earth.
Which planet seems to move faster when viewed from
Earth? Explain.
CHALLENGE
6. Predict Suppose that you are standing at the North Pole
on a dark night. If you keep turning clockwise at the same
speed as Earth's rotation, how would your movement
affect your view of the stars? (If…, then…, because...)